Spark plug with enlarged cooling chamber



March 7, 1,939. A. E ANDERSON SPARK PLUG WITH ENLARGED COOLING CHAMBER Filed Sept. 27, 1937 gin ow Wait-Jam v Patented Mar. 7, 1939 PATENT OFFICE SPARK PLUG WITH ENLARGED COOLING CHAMBER August Eugene Anderson, Montclair, N. J.

Application September 27, 1937, Serial No. 165,975

4 Claims. (01. 123169) My present invention relates to spark plugs with enlarged cooling chamber and forms an improvement and further development of the spark plug shown and described in my Patent 2,071,450

issued February 23, 1937.

Beside the advantage possessed by my said patented spark plug, namely: a permanently set and correctly adjusted spark gap which is arranged far back in the metalhousing and above the water jacket; I claim for this improved spark plug, also the particular advantage of an enlarged porcelain cooling chamber with a flexible mica washer therein. The latter is so positioned in the cavity of the cooling chamber that free space is provided both above and below the mica washer. This will prevent all deposit of carbon, because the latter will not collect on a flexible surface, whereas it has been found that it will do so on unyielding or solid walls, whether metal, porcelain or mica. This drawback is found in all ordinary types of spark plugs having the insulating surfaces exposed to burnt gases mixed with oil. The improved spark plug is thus proof against fouling as no electric current can pass between any parts of the metal housing and the porcelain cooling chamber, but only over the spark points.

Another object of the mica washer is to completely insulate the poreclain cooling chamber from the metal part of the spark plug shell so that no electric spark or leakage may proceed to the metal part of the spark plug shell.

Still another advantage possessed by my improved spark plug consists in the feature that the flexible mica washer serves to cool the chamber cavity of the insulator at all times and as a consequence keeps the insulator and its central electrode much cooler than in the ordinary types of spark plugs. Fouling and pre-ignition are thus prevented and it has been found that one size and shape of porcelain or insulator, when constructed as herein outlined, will serve most, if not all, of the various types of combustion engines. In the accompanying drawing, one embcdiment of my invention has been illustrated.

Fig, 1 is an axial section of the improved spark pl Fig. 2 is a cross section along line 22 of Fig. 1;

Fig. 3 is a plan view of the mica washer;

Fig. 4 is a cross section of the combination gasket and ground electrode; and

Fig. 5 is a plan View of Fig. 4.

In the drawing the same reference characters refer to the same parts in all the figures.

Reference numeral III represents the metal housing or shell of the spark plug with an externally threaded shank at its lower end for securing the plug in position in the cylinder head of a combustion engine, and an internal thread at its upper end engaging the securing nut I I for retaining the insulator or porcelain I2 in the housing. Above the shank portion of the housing, a flat shoulder I3 is formed constituting a seat for the enlarged body portion I4 of the in- 10 sulator I2. Except for this flat seat in the housing the construction so far is similar to that described in .my above named patent.

The body portion I4 itself of the porcelain has a deep, inverted V-shaped annular cavity I5 15 which constitutes an extension to the main explosive chamber I6 of the spark plug and into which main chamber the body portion I4 does not project, terminating, as it does, with a flat shoulder I1, thereby differing from my said patent. The inner tapering wall of said cavity is however extended to reach about half-way into said main chamber and forms a central cone I8 of the porcelain insulator I2. Through the whole length of the insulator is provided a bore containing the main electrode I9 which protrudes slightly below the pointed end of the cone l8 and constitutes one of the spark points 2!] in the plug.

On the seat I3 is placed a combination metal gasket and second electrode consisting of a flat ring 2| with a finger 22 projecting from the inner periphery of the ring and bent down and center wards to terminate with the second spark point 23 opposite the main spark point 20.

Above this gasket and directly under the shoulder I! of the insulator is placed a washer 24, preferably made of mica or similar heat insulating material. This washer has an exterior diameter about the same as that of the body IA of the insulator I2 and of the gasket I3. Its inner diameter is, however, less than that of said members but enough larger than that of the cone I8 at the same level as said washer 24 in order to permit free circulation of gases between the main and the extension chambers I6 and I5. In this manner said washer 24 projects inwardly beyond the inner edge of the gasket 2| and that of the flat shoulder I'I, both of which have substantially the same size openings. By now using washers 24 of the very thinvmica, so as to make them very flexible, and providing free space above and below the same, the main feature of this invention is gained, namely the prevention of carbon deposit in the cooling chamber. The constant vibration of this flexible washer will prevent any carbon to collect thereon or on the walls of the adjacent cooling chambers, because of the fact that carbon will deposit only on solid, unyielding surfaces. This flexing of the mica washer will also cause continuous movement of the gases in and out of the extension, cooling chamber, thus still further aiding in the cooling of the insulator and of the main electrode therein.

The mica washer 24 and the electrode gasket 2| are preferably permanently secured under the insulator shoulder I! to form a unit therewith and with the main electrode I9. In this manner I gain the advantage that in case of breakage, the broken insulator unit may easily be removed and immediately replaced by another unit, which is already adjusted as regards distance of spark points. Thus no extra fitting is required since the spark gap has been previously and permanently set for proper functioning of the spark p Other features and advantages of my improved spark plug may also be mentioned, such as: the fact that the spark-gap is placed far back in the main cooling chamber l6 and above the water jacket. This gives good protection for the end of the porcelain insulator and prevents its cracking. Further protection against cracking is also gained by the fact that the main portion or body of the insulator terminates at its seat in the housing, which has the added advantage of considerably increasing the volume of the cooling chamber.

It is to be understood that the invention is not limited to the details of construction here shown and disclosed, but that these may be varied widely without departing from the spirit of the invention as defined by the claims.

I claim:

1. In a spark plug, a metal housing having a bore therethrough with a flat shoulder forming a seat, a porcelain having a flat ended body portion adapted to be seated on said shoulder, an annular cavity formed in said body and opening downwardly into a main cooling chamber provided'below said seat in the metal housing, a central cone on said porcelain body projecting about midway into said main cooling chamber, a main electrode carried by the porcelain and projecting slightly'beyond the apex of the cone and constituting the main spark point, a flat metal gasket in said seat having a downwardly extending finger constituting a second spark point terminating about level with said main spark point, and a thin mica washer inserted between said flat body and said gasket and providing a narrow passage around said cone between said cavity and main chamber.

2. In a spark plug, a metal housing having a bore therethrough with a fiat shoulder forming a seat, a porcelain having a flat ended body portion adapted to' be seated on said shoulder, an annular cavity formed in said body and opening downwardly into a main cooling chamber provided below said seat in the metal housing, a central cone on said porcelain body projecting about midway into said main cooling chamber, a main electrode carried by the porcelain and projecting slightly beyond the apex of the cone and constituting the main spark point, a flat metal gasket in said seat having a downwardly extending finger constituting a second spark point terminating about level with said main spark point, and a thin mica washer inserted between said flat body and said gasket and providing a narrow passage around said cone between said cavity and main chamber, said gasket, washer and porcelain with the main electrode being firmly connected to form a replaceable unit with preadjusted spark gap.

3. In a spark plug, a metal housing having a bore therethrough with a shoulder forming a seat, a flat ended porcelain adapted to be seated on said shoulder, an annular cavity formed in the flat end of the porcelain and opening into a main cooling chamber provided in the housing, a central cone on said porcelain projecting into said chamber, a main spark point carried by the porcelain and projecting slightly beyond the apex of the cone, a flat metal gasket in said seat carrying a second spark point terminating about level with said main spark point, and a thin, heat resisting flexible washer inserted in said seat between the flat faces of the porcelain and the gasket and having a central opening providing a narrow passage around said cone between said cavity and main chamber.

4. A spark plug comprising a metal housing and a dielectric said housing having a bore with a seat for the dielectric and a cooling chamber below said seat, a central cone on said dielectric protruding beyond said seat about midway into said cooling chamber and a main spark point at the apex of said cone, an annular cavity formed above said seat around the cone constituting an auxiliary cooling chamber, a second spark point extending from said seat to the vicinity of said main spark point, and vibratory means of heat insulating material disposed between the two chambers permitting free passage between them, whereby deposits of carbon will be prevented by said vibratory means.

AUGUST EUGENE ANDERSON. 

